This Program links basic research in analysis of public health records, measurement of mutations and cell kinetics in dissected human lungs, studies of the mutagenic effects of airborne toxicants at dose levels mimicking the human lung, measurement of the broad set of DNA adducts, derived from airborne toxicants and analysis of particle in human lungs and the study of the sources and basic mechanisms of formation of the primary human cell mutagens found in urban air. Together we are testing the hypothesis that exposure to combustion generated airborne toxicants mutate or otherwise change the cell kinetic behavior of human lung cells so the rate of lung cancer is increased in the American population.